Joshua D. Drake wrote:
On 09/13/2011 09:12 PM, Michael Bayer wrote:
On Sep 13, 2011, at 9:15 PM, Joshua D. Drake wrote:
conn=psycopg2.connect("dbname='foo' user='dbuser', AUTOCOMMIT=TRUE)
cur = conn.cursor()
cur.execute("""INSERT""")
cur.execute("""SELECT * from bar""")
cur.begin()
cur.execute("""INSERT""")
cur.commit()
cur.close()
Is much better than:
conn=psycopg2.connect("dbname='foo' user='dbuser', AUTOCOMMIT=TRUE)
cur = conn.cursor()
cur.execute("""INSERT""")
cur.execute("""SELECT * from bar""")
cur.execute("""BEGIN""")
cur.execute("""INSERT""")
cur.commit()
cur.close()
what's wrong with:
conn = psycopg2.connect(....)
cur = conn.cursor()
cur.execute(" ... sql ...")
conn.commit()
Nothing, that doesn't actually do anything I didn't suggest above.
? if one wants to work with transactions, DBAPI in it's default
mode provides that.
Correct.
If you want all statements to be ad-hoc such that they are
"committed" immediately, whether that means COMMIT after every
statement as it does on Oracle or just no BEGIN emitted as it does on
Postgresql, turn on "autocommit". "autocommit" is a flag you should
only be able to change when no transactional state has otherwise
accumulated, but otherwise, switch it any time.
Yes.
Adding explicit begin() means the DBAPI starts to look confused as to
how it should be used - DBAPI authors also have to support two
different transactional styles.
No. What I am saying is, the begin() is optional. If you look at my
example, if PostgreSQL is in autocommit mode, the only way to start a
transaction is to execute a query to start the transaction (BEGIN or
START TRANSACTION). From a, "it would be nice if" perspective, I would
like to have the option of using .begin() to start a transaction. That
seems to jive better with proper coding.
I think the semantics you are describing are:
1. auto commit mode is on
2. whilst in auto commit mode the user wants to start a transaction
that will not be autocommit
The above is a guess I'm making, ;-) Those semantics are very different
to other DBMS implementations and maybe why there is some confusion over
the suggestion.
Chris
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